Chemical modification of coal into hydrocarbon oils and coke



July 26, 1955 Filed March 6, 1951 E. BLEMN R CHEMICAL MODIFICATION HYDROCARBON OILS AND COKE F COAL INTO 2 Sheets-Sheet l A ttorney5 July 26, 1955 E. BLUEMNER 2,714,086

CHEMICAL MODF:[C'ONv OF COAL INTO HYDROCARBON OILS AND COKE 2 Sheets-Sheet 2 Filed March 6. 1951 A Horn e yd.

United States Patent O CHEMICAL MDIFICATION F CGAL INTO HYDRCARBN OILS AND COKE Erwin Bluemner, Munich, Germany Application March 6, 1951, Serial No. 214,069 6 Claims. (Cl. 19o-56) This invention relates to the chemical modification of coal. One ofthe objects of the invention is to provide a method for the treatment of bituminous coal, which per-` mits consideraole amounts of liquid hydrocarbons to be obtained. per unit of coal. Another object is to provide a method for the production of liquid hydrocarbons from bituminous coal in Which the solid residues are obtained in the form of hard, marketable coke. A further object is to provide a methodfor preparing a liquid extract from bituminous coal. A still further object is to provide a new method for transforming the greater part of bituminous coal into a substance which is soluble in oil. Other objects and features of the invention will become apparent as this specication proceeds.

It is Well known that the carbonisation of coal in gasproducing retorts, in addition to supplying a combustible gas and coke, also yields certain quantities of hydrocarbons that are liquid at ordinary temperatures.` it is also known in the so-called low-temperature carbonisation to conduct the carbonisation of coal at a temperature lower than that used for example in most gas works or in colte ovens, and although this low-temperature carbonisation yields an increased output of liquid hydrocarbons, a high percentage of the hydrogen content of the coal is, even with this process, obtained in the form of permanent gases.

It is, on the other hand, known to subject petroleum and other hydrocarbon oils to a so-called pressure-cracking,

whereby a relatively high percentage of the hydrogen content is obtained in the form of low-boiling liquid hydrocarbons.

Investigating the problems of the utilisation of coal with a particular view to obtaining a high yield of low-boiling liquid hydrocarbons, I have found that any coal has predetermined transformation temperatures, which are approximately at 300, 380 and 400 C. respectively, and that the transformations occurring at each of these temperatures require a certain amount of time to become eifective. More particularly I have found that any coal (of bituminous character), at two temperature ranges lying respectively between approximately 280 and 310 C. and between approximately 390 and 410 C. will split off gases and become softened, and that if such temperatures are successively maintained under sufliciently high pressure for example a pressure in excess of l g./cm.2 for a suiiciently long time it is possible to dissolve the coal in suitable oil, while this solubility is not obtained when the mass of coal is raised by continuous heating to temperatures above 400 C. It must be pointed out that in its original condition coal does not contain any volatile substances capable of being simply expelled by the action of heat, and that any modification of the coil, either by `hydrationl or by carbonisation under ordinary or increased pressure, is only made possible by preliminary resolution or transformation of the coal into reactive decomposition products. If the resolution or transformation is to extend throughout the mass of the coal, it is necessary for the transformation temperatures (approximately at 280 to 310 C. and at 390 to 410 C. respectively) to be observed during the heating and each to be maintained for an adequate time. Unless the coal is thoroughly transformed in this manner, one cannot, since the basic substances for oil synthesis are charac-` terised by solubility in oil, exceptto obtain oil yields which to any extent equal the inherent possibility of oil formation. v

From this consideration it will be understood that working conditions in an ordinary low-temperature carbonisation furnace are unsuitable, and cannot be made suitable, for this purpose because within such a furnace there are differences in temperature beyond any possibility of measurement and reaching several hundred degrees. Not only the above-mentioned resolution or transformation of the coal substance is a process which can only be successfully carried out if the required temperatures and times of reaction are carefully maintained, but such accurate maintenance of temperatures and times of reaction is necessary to an even higher degree for the subsequent hydrogenating synthesis of the medium and light hydrocarbons, since the temperatures of this synthesis are closely below the maximum temperatures above which hydrocarbons tend to become rapidly decomposed into permanent gases and carbon, i. e. the ultimate products of pyrogenous decomposition.

Another factor contributing to the low yield of liquid hydrocarbons in carbonisation furnaces is the fact that in these furnaces the formation of coke takes place in the same chamber in which the synthesis of oil is to be effected, so that the dehydrating characteristics ofthe coke being formed interfere with the formation of oil. It is therefore a further object of the invention to provide an improved method and apparatus whereby the compound influence of this and other detrimental factors can be minimised.

With this and other objects in view the invention, in one aspect consists in converting the greater portion of coal into an `oil-dissolved extract and subjecting such oildissolved extract to pressure cracking. It is only this extract which makes it possible to hydrate one portion thereof at the expense of the hydrogen of another larger portion thereof. A

According to a further feature I provide the coal as a finely ground powder, and also provide an oil, prepare a suspensionof said powder in said oil, heat said suspension to a temperature equal to or slightly in excess of the minimum reaction temperature and maintain it at such temperature until a maximum of solubilisation is substantially reached and an extract is obtained which comprises up to ofthe original coal in solubleform. In practice, in order to obtain a satisfactory degree of conversion of the coal into oil-soluble extract, a two-` stage process is preferably employed in which a suspension of pulverised coal in a suitable carrier oil is first heated to a temperature of 290 to 300 C. and maintained at this temperature, while being agitated, for a period of, for example, half-an-hour, thus converting part of the coal into soluble extract substances, the mixture being then raised to a temperature of 390 to 410 C., and, while again being agitated, being maintained at such temperature for asimilar period, during which a further As already stated, this extract is according to a further feature of the invention, subjected to conditions of a pressure thermic treatment analogous to the pressure cracking of oils. When this process is completed, the pressure is released to obtain separation into on the one hand the mineral oils of high hydrogen content obtained from the mixture of coal and carrier oil, these being further separatedby fractional separation (condensation) and onthe other hand the residues poorest in hydrogen and being pitch substances, which latter are then subjected to a'heat treatment without pressure for obtaining coke.

It is thus a further object of the invention to provide a continuous process for the production of hard coke and simultaneous production of a high output of light and medium hydrocarbons from bituminous coal of any kind and more particularly from bituminous coal having such chemical and physical characteristics as would prevent a marketable hard-coke from being obtained in the customary louI temperature carbonising methods. While part of the apparatus for carrying out this method may be similar to the apparatus described in my earlier Patent No.-2,144,178, a method in accordance with the present invention and suitable apparatus for performing the same will now be described more in detail by way of example with reference to the accompanying drawingsy in which:

Fig. 1 is'a diagrammatic view of one form of apparatus according to the invention, incorporating a flow diagram;

Fig. 2 shows a modified form of part of this apparatus;

Figs. 3 and 4 are a fragmentary axial section and a cross-section respectively of a reaction cylinder, and

Figs. 5 and 6 are corresponding views of a heating cylinder.

Referring now to the drawings, coal from a bunker 1 is admitted through a pipe 2 to a pulverising mill 3, which converts the coal into a fine powder preferably a powder passing through a 1000 to 1300 mesh (150-200 per sq. cm.), no appreciable advantages being obtainable by comminution beyond this degree of neness. The powder obtained in the mill 3 flows through a pipe line 4 to a container 5 for the pulverised coal; the latter supplies the pulverised coal to a mixing device 6, to which heavy mineral oil measured by a device 8 is simultaneously admitted to produce suspension of thev coal in the oil. Now, in accordance with the invention, the paste-like mixture of coal and oil is now subjected to the gentlest p ossible resolving transformation to produce a selected extract. For this purpose the mixture obtained in the mixer 6, which by means of a pump 9 has been transferred to a storage tank 10, in which it is stirred by a motor 11, is forced by a pressure pump 12 working against a pressure of more than 20 kg./cm.2 through the coil 13 of a heat exchanger 14 into the lower end of a first heating .cylinder 15 which forms one of a battery of cylinders` in a suitably heated reaction furnace 16. The cylinder 15 contains a cylindrical rotor 17 which, as seen more clearly in Figs. 5 and 6, fills the cylinder except for a narrow annular space along the Wall thereof. The rotor 17 is mounted on a shaft 18 which extends through the upper cover 19 of the cylinder and is driven for rotation jointly with'similar rotors in all remaining cylinders of the furnace 16, by means of a geared motor 20 and a transmission shaft 24. The rotor 17 carries three longitudinally extending Scrapers 21 which move in contact with the cylinder wall and force the material in the cylinder to participate in the rotation of the rotor while passing upwardly between the latter and the wall of the cylinder. The heating of the cylinder 15 is so controlled in relation to the rate of movement of the mixture into each cylinder, the distance between the rotor and the cylinder wall and the speed of rotation of the rotor, that the temperature of the mixture will rise in the cylinder 15 to the rst reaction temperature of 290 to 300 C., the arrangement being such that, owing to the small cross-section of the annular space between the cylinder wall and the rotor, this heating takes place at a rapid rate as to be completed, for example, within 7 minutes. From the upper end of the cylinder 15 the heated mixture is conducted through a pipe connection including a vertical gas-separator pipe 22, which will be described further on, to the lower end of the next following cylinder 23. The latter is generally of similar construction as the cylinder 15 and likewise contains a rotor driven synchronously with the rotor 17 by the common transmission shaft 24 but, as seen more clearly in Figs. 3 and 4, this rotor 25, has a substantially smaller diameter than the rotor 17, while the cylinder 23 has the same diameter as the cylinder 15. As a consequence, the annular space between the rotor and the cylinder 23 has a much greater cross-section area than the annular space between the first cylinder 15 and its rotor 17, and as a consequence the speed at which the mixture arriving from the pipe 22 rises through the cylinder 23 is substantially less than the speed at which the mass rises through the cylinder 15, the dimensions being such that the material remains in cylinder 23 for a period of approximately minutes. Scraper arms 26 making contact with the wall of the cylinder 23 are provided on the rotor 25 similarly to the Scrapers 21 on the rotor 17, these Scrapers being however modified in dimensions and construction in accordance with the greater width of the gap between the rotor and cylinder wall. The circumferential speed at which the Scrapers move over the surface of the cylinder wall is substantially greater than the speed at which the material rises in the cylinder, so that, in spite of the diierence in the rate of vertical movement of the material in the two cylinders which corresponds to the different periods in which the material is intended to stay in each of these, the speed at which the material is moved along the wall, which is of great importance for the transfer of heat, is substantially the same. The heating of the cylinder 23 is so controlled that during the 30 minutes period in which the material remains in this cylinder its temperature rises only to 310. From the upper end of the cylinder 23 the material is conducted through a pipe connection 27, similar to pipe connection 22, to a further cylinder 15a which is of substantially the same construction as cylinder 15, and from the upper end of which a pipe connection 28 leads the material to a further cylinder 23a, substantially identical in construction with cylinder 23. Further pipe connections 29 and 30 respectively serve to conduct the material from cylinder 23a to a cylinder 15b, substantially identical with cylinder 15 and thence to a last cylinder 23h, substantially identical with cylinder 23. In cylinder 15a the material is rapidly heated to 390 C.. while in cylinder 23a it remains for a period of about 30 minutes, during which its temperature is raised from 400-410.

The treatment in cylinder 23a completes the conversion of the coal into oil-soluble extract substances dissolved in the carrier oil, and the solution thus obtained is now ready to be subjected to treatment corresponding to the cracking of liquid hydrocarbons. To this end the material coming from cylinder 23a, after being freed from gases during its passage through gas separator pipe 29, is rapidly heated in cylinder 15b to a temperature of about 450 to remain in cylinder 23h for a further period of 30 minutes during which it is gradually heated to 470 C. A further pipe connection 31 leads from cylinder 23b to a pressure-release valve 32 in which the pressure of the treated material is reduced from its previous value of approximately 20 kilograms per square centimetre to atmospheric pressure, at which it is allowed, through a stop valve 33, to enter a coking retort 34 which has previously been brought to a temperature of about 400 to 500 C. Owing to the sudden reduction of pressure, on entering the retort 34 the volal tile components will at once evaporate, the temperature ofthese components being prevented by the evaporation from rising above 400 C. The vapour mixture, which in practice will have a temperature of 350 to 400 C., passes through a further 'stop valve 35 to enter a separating column or dephlegmator 36. The lightest fraction containing benzine and permanent gases is led off through a pipe 37 at the top of the column to a benzine condenser 38, a water remover39 and 'gas washer 40, whence the permanent gases are led through a pipe 41 to the gasometer 42. Gas from this gasometer isutilised for heating the reaction furnace 16 and the retort 34, to which it is supplied through a pipe system 43. Crude benzine from the benzine condenser 381is collected in a tank 44. i The heavier fractions are conducted from the column 36 through different pipe connections, viz.v medium oil (diesel oil) through a pipe connection 45 to a cooler 46 and a medium oil tank 47, while heavy oil, which has the highest condensation temperature, is conducted through a pipe 48 and through the body of the heat exchanger 13 before being finally cooled ina cooler 49 and stored in the heavy o'il storage tank 50. This heavy oil can, according to a feature ofthe invention, be used as the oil to be mixed with the car-` bon dust to form the initial suspension, and for this purpose it is fed from the tank 50 by a pump 51 through a feed line 52 to the measuring device `8 tore-enter the` circuit. The apparatus, 'asso far described, is allowed to operate until an appropriate Aquantity of carbonaceous residue has been accumulated in the retort 34. In order that this residue may rnow be converted into a marketable hard coke and at the same time the continuity of the process be maintained, additional retorts 34a, 34h, 34C, constructed andl arranged to be heated similarly to retort 34, are provided,as schematically indicated in the drawing, each of these furnaces being connected through branch pipes including stop valves 33a, 33b, 33C, and 35a, 35h, 35C (corresponding to valves 33 and 35 respectively) so that by operating thevvalves the delivery of material from the pressure-release valve 32 can be selectively transferred to any of the retorts provided, this retort being simultaneously connected to the inlet of the separating column 36 to maintain the continuity of the process. The filled retort 34 which has been disconnected from the reaction furnace 16 isthen heated to a higher temperature to cause `the substantially pitch-like residue to be converted into coke; since the temperature to which this retort is heated will not alect the previously produced liquid hydrocarbons, since these have already left the retort, this nal coking` temperature can be selected in accordance withv the desired quality of coke and may, for example, be between 500 and `1000 C. During this iinal stage of heating a certain amount of gas will still be liberated which is admitted to the column 29. While one retort is being filled and a second heated to convert the residue into coke, the third retort may be discharged and "the fourth brought back to the proper pre-heating temperature for kvreceiving the material discharged from the cylinder fur-` nace.

Referring now to Figs. 3 to 6, the connection between each `cylinder or 23 etc. and the gas separator pipe 22, 27, etc. is eifected by a pipe connection`54 by which the liquid material is removed therefrom, and whichvextends through the top of the cylinder to approximately the upper level of the rotor thereof. The level 55 of the liquid material in each ofthe `cylinders is initially held at some distance from the upper end of the cylinder by introducing a quantity of gas under pressure before the beginning of the operation.4 Each rotor r17 or `2,5 etcris formed as a hollow body, theinterior of which normally communicates vwith [the gas-` v filled space above the level 55 ofthe material through a J-shaped tube 56, thusensuring that thepressure inside the rotor is equal to the pressure in the cylinder while preventing the material to `be treated from enteringth'e interior of the rotor. Moreover, the curved upper end of each tube 56 is provided with a iloat valve 57 which will automatically close if the level of the material rises beyond the predetermined limit. Safety valves 58 are further provided in connection with each of the downwardly leading pipes 22 etc. adjacent the junction with the pipes 54 which, should the pressure in any of the cylinders rise beyond a predetermined maximum, open a connection to a pipe 59 leading into the separating column 36. During the heating of the material gas including vapours and/ or permanent gases is liberated in each cylinder and tends to accumulate at the upper end of the cylinder. The liquid level 55 is thereby forced down until it reaches the end of the pipe 54, whereafter gas will escape through the pipe 54, together with the liquid material, at the same rate as it is liberated. It is ultimately separated from the liquid material as the latter descends along each gas separator pipe 22, 27 etc. As shown in Figure 3 the valve element of each safety valve 58 has a gas escape passage which is controlled by a needle valve 62 carried by a float 63 in the gas separator pipe, and which will allow gas to escape through pipe 59 to the separator column irrespective of pressure, whenever the liquid level in the separator pipe falls below a predetermined level. The pipe 59 may additionally be utilised by applying pressure to a point 60 thereof and temporarily closing a stop valve 61, for supplying initially to the individual cylinders 15, 23 etc. gas under pressure to ensure the desired height ofthe level 55. The pressure in all the cylinders is, as already mentioned, maintained at, at least, 20 kilograms per square centimetro, and may, for example, be 25 kilograms per square centimetre, in order to avoid` evaporation of the volatile hydrocarbons prior to the pressure release by valve 32 and also in order to control the decomposition of the mixture towards the creation of relatively large molecules, thus ensuring a relatively large output of desired liquid hydrocarbons as compared with permanent gases. The safety valves 58 are loaded by weights 64 so as to open at a pressure which is 3 to 5 kilograms per square centimetre higher than the normal-working pressure of the appaatus to which release valve 32 is adjusted.

In practice the cylinders may, for example, have a diameter of one metre, the diameters of the rotors 17 and 25 being 90 centimetres and 50 centimetres respectively; in this case, the time for which the material remains in the cylinders 15, 15a, and 15b is approximately one quarter of the time for which the mixture remains in cylinders 23, 23a, and 23b, so that the liquid may remain for 7 minutes in each of the iirst mentioned cylinders and for 28 minutes in each of the last-mentioned cylinders. The rotors may, in this case, be driven at a speed of l5 revolutions per minute corresponding to a circumferential velocity of the material of approximately 75 centimetres per second, while the speed at which the mixture moves axially through the cylinders may be of the order of only one or a few centimetres persecond. j Y

While the apparatus described is highly. suitable, for carrying out the method according to the present invention, the apparatus may be modified in various details in accordance with the requirements from case to case. If desired, the rapid heating before and between the individual reaction periods may, instead of being effected in the cylinders 15a, 15b, be effected in flow heater furnaces containing a coil through which the mixture is conducted. Fig. 2 shows an embodiment of this nature in which the cylinders 15, 15a, 15b in the furnace 16 are replaced by pipe coils 150a, 150b respectively in a rapid heating furnace which is likewise adapted to be heated by gas supplied through the pipe system 43.

It will be observed that in the process described bituminous coal is first ground to a powder, if necessaryl tion.

freed'of ash, for example by otation or by electrostaticV v means, and then mixed with heavy oil to form a suspen` sion. The obtained paste consisting of a suspension of coal dust in oil is then subjected to the gentlest possible decomposition by selective extraction. The resulting coal extract is no longer identical with the untreated coal but exhibits pronounced reactivity, and Vstill contains practically the entire hydrogen content of the coal` What is actually obtained is a solution of extract in oil, whichV contains undissolved matter from the coal substance amounting to l to 20% of the coal. This solution is then rapidly heated, in bulk, to a moderate cracking-temperature and kept at this temperature until a thorough breaking down of the extract, which is unstable at this temperature,` has takenplace, these two steps being repeated if necessary once or several times at progressively higher reaction temperatures. Y

All these reactions, that is to say the decomposition of thel coal substance to form an extract, the breaking down of this latter, and molecularregrouping reactions yielding more stable compositions, are carried out under a pressure in excess of atmospheresabove atmospheric pressure. The products resulting from the breaking down of the extract solution under pressure, which contained the so-called volatile constituents of the coal still in combined form, are of a different nature from the gases and tarry vapours obtained by low temperature carbonisa- It is an essential feature of the present process that the breaking down of the extracts under pressure is carried out with the entire mass kept at a uniform ternperature and in the complete absence of semi-coke or coke formed in the course of the process.

It is well known that in the course of cracking hydrocarbons a portion thereof is subjected to hydrogenisation at the expense of the hydrogen content of another portion, and the lower the hydrogen content of an oil the greater the de-hydrogenated portion of4 that oil will be. In consequence of the low hydrogen content of the coal extract in the present process, this phenomenon occurs here in an intensified degree.

The regrouping process may be controlled by the addition of catalysts, and in this manner therultirriate products obtained may be considerably improved, more particularly as regards their octane value and the'presence of a higher percentage of aromatic components in the benzine fraction. For this purpose aluminum silicates and magnesium silicates may with advantage be employed as catalysts in accordance with the so-called Huid-catalyst method well known to those skilled in the art; the catalyst may advantageously be added to the carbon-in-oil suspension before the latter is heated for conversion.

Although the benzine yield of the processwill not be directly improved by the use of such catalysts, it is nevertheless possible to increase this yield by re-circulating the gas-oil fraction into the cracking stage to be cracked once more, and somewhat lower temperatures may be employed for the cracking.

After completion of the reaction whereby the coal extract is broken down under pressure, the resulting product is separated into its hydrogenated and de-hydrogenated constituents, by blowing the entire reaction mixture Vinto pressureless pre-heated retorts. In the conditions of temperature reduction brought about by evaporation of the hydrocarbons, all that remains in the retorts are the non-distillable products of low and lowest hydrogen content. These products consist substantially of substances which do not go into solution in the extraction stage, residues containing practically pure carbon and resin and pitch-like matter formed in the stage in which the extract is broken down under pressure. The last named constituents are the substances which effect the cementation of the nascent coke. The coke is generated by a further heating of the lled retort, which is eifected while the filling of a second, third and subse- 8 quent retort isin progress. The temperature to which the retorts are heated may be between 500 and 1000 C. and is determined not by the coal used but by the required quality of the coke yield.

The distillable products leave the retort that is being charged at the moment of their evaporation, at a temperature below 400 C., so that no pyrogenic decomposition of these products can take place. They are collected, in a fractional condensation stage, in the form of heavy, medium and light oils which are free of dust and transparently clean. Y

The operation of this process is variable by employing a mixture of oils for preparing the starting suspension of coal dust in oil. As a general rule, however, at least the main constituent of the mixed oil used for this purpose is an oil of medium hydrogen content such as the described plant itself produces as its heavy oil condensate, since oils of low or medium hydrogen content have been found to be the best solvents for the selective extraction. The course of the proces can also be controlled by adding to the mixed starting oil, oils of high hydrogen content which exert a hydrogenating eect in the cracking stageV and which cause hydrogen or atomic groups rich in hydrogen to become incorporated in the readily receptive products of the breaking down of the coal extract. Instead of being added to the mixing oil, such oil may be fed at an appropriately elevated temperature, to the extract in the cracking stage. In any case, the addition of such oil and its participation in the breaking down reaction increases the light oil yield, with reference to the quantity of coal treated.

The selective extraction is effected by rapidly heating the coal paste, under a pressure of at least 20 atmospheres, to a partial decomposition temperature and maintaining itat this temperature until the respective decomposition reaction is completed. The mass is then rapidly heated to the next decomposition temperature and again kept at this temperature until the reaction is completed. Immediately following completion of the last extraction stage, the breaking down (cracking) process is initiated.

The apparatus herein described is distinguished from that of my earlier Patents Nos. 2,131,308 and 2,144,178 by the fact that the rotors situated in alternate pressure cylinders are made with differing diameters so that the annular space formed between them and the cylinder wall is larger when the rotor is of smaller diameter and smaller when the rotor is of greater diameter, whereby the required rapid heating of the treated mass is effected in the passage of the mass through the narrower annular space, and the retention for a protracted period at elevated temperature in the wide annular space. The vertical scrapers attached to the rotors impart to the reaction mass, in the heating-up and prolonged-heating phases, the requisite turbulent movement and rate of flow in a horizontal Adirection relatively to the cylinder wall.

' I claim:

1.` A continuous process for the production of light and medium hydrocarbon oils and hard coke from bituminous coal which consists in mixing the coal in finely comminuted form with a heavy oil to form a paste mixture, forcing the mixture through a continuous enclosed passage comprising a plurality of successively arranged treatment zones, maintaining a pressure of at least ofthe order of 20 kg./cm.2 in said enclosed passage whilst the mixture is forced therethrough, heating the mixture rapidly to a temperature approximating to the lowest conversion temperature of the coal whilst it is passing through a iirst treatment zone, applyingjheat at such a rate to thermixture whilst it is continuously passing through a second treatment zonev of larger volume than said first treatment zone that the temperature of the mixture will be maintained substantially at said lowest conversion temperature, the volume of said second treatment zone being such that the conversion at said temperature will be substantially completed during artrose the passage of the mixture through said second treatment zone, applying heat at such a rate to said modied mixture as it passes continuously through a third treatment zone of smaller volume than said second treatment zone that the temperature of the modified mixture will be raised during its passage through said third treatment zone to a temperature approximating to a higher conversion temperature of the coal but below the cracking temperature, applying heat at such a rate to the modified mixture whilst it is continuously passing through a fourth treatment zone of larger volume than said third treatment zone that the temperature of the modified mixture will be maintained substantially at said higher conversion temperature, the volume of said fourth treatment zone being such that the' conversion at said higher conversiontemperature will be substantially completed during the passage of the modified mixture through said fourth treatment zone, applying heat at such a' rate to said further modified mixture as it passes continuously through a fifth treatment zone of smaller volume than said fourth treatment zone that the temperature of the further modied mixture will be raised during its passage through said fifth treatment zone to a temperature approximating to a cracking temperature, applying heat at such a rate to the further modified mixture whilst Vit is continuously passing through a sixth treatment zone of larger volume than said fifth treatment zone that the temperature of the further modified mixture will be maintained substantially at said cracking temperature, the volume of said sixth treatment zone u being such as to permit cracking at such temperature to be substantially completed during the passage of the mixture through said sixth treatment zone, discharging the cracked mixture from said sixth treatment zone with release of pressure into one of a plurality of retorts whilst removing and separating the volatile components from the non-Volatile residues until the retort is filled to the desired extent whereupon the cracked mixture is discharged into a further one of said retorts, heating the filled retort to heat the non-volatile residues therein to a coking temperature andA release further volatile components, collecting the volatile components, and removing the formed coke from said retort.

2. A continuous process for the production of light and medium hydrocarbon oils and hard coke from bituminous coal which consists in mixing the coal in finely comminuted form with a heavy oil to form a paste mixture, forcing theV mixture through a continuous enclosed passage comprising a plurality of successively arranged treatment zones, maintaining a pressure of at least of the order of 20 kg./cm.2 in said enclosed passage whilst the mixture is forced therethrough, heating the mixture rapidly to a temperature approximating tothe lowest con- Version temperature of the coal whilst it is passing through a first treatment zone, stirring the mixture whilst it is passing through said firsttreatment zone, applying heat at such a rate to the mixture whilst it is continuously passing through a second treatmentzone of larger volume than said rst treatment zone that the temperature of the mixture will be maintained substantially at said lowest conversion temperature, the volume of said second treatment zone being such that the conversion at said temperature will be substantially completed during the passage of the mixture through said second treatment zone, stirring the mixture whilst it is passing through said second treament zone, allowing gaseous constituents of the resulting modified mixture to separate from the liquid constituents thereof and withdrawing said gaseous constituents without releasing the pressure on the modified mixture, applying heat at such a rate to said modified mixture as it passes continuously through a third treatment zone of smaller volume than said second treatment zone that the temperature of the modified mixture will be raised during its passage through said third treatment zone to a temperature approximating to a higher conversion temperature of the coal but below the cracking the modified mixture whilst it is passing through saidfourth treatment zone, allowing further gaseous constituents of the resulting further modified mixture to separate from the liquid constituents thereof and withdrawing the said further gaseous constituents without releasing the pressure upon said further modified mixture,

applying heat at such a rate to said further modified mixture as it passes continuously through a fifth treatment zone of smaller volume than said fourth treatment zone that the temperature of the further modified mixture will be raised during its passage through said fifth treatment zone to a temperature approximating to a cracking temperature, stirring the further modified mixture whilst it `is passing through said fifth treatment zone, applying heat at such a rate to the further modified mixture whilst it is continuously passing through a sixth treatment zone of `larger volume than said fifth treatment zone that the temperature of the further modified mixture will be maintained substantially at said cracking temperature, the volume of said sixth treatment zone being such as to permit cracking at such temperature to be substantially completed during the passage of the mixture through said sixth treatment zone, stirring the mixture whilst it is passing through said sixth treament zone, discharging the cracked mixture from said sixth treatment zone with release of pressure into one of a plurality of retorts whilst removing and separating the volatile components from the non-volatile residues until the retort is filled to the de-' sired extent Whereup the cracked mixture is discharged into a further one of said retorts, heating the filled retort to heat the non-Volatile residues therein to a coking temperature and release further volatile components, collecting and condensing the volatile components into light,

medium-light and heavy liquid hydrocarbons, removing the formed coke from said retort, and feeding back at least part of said condensed heavy liquid hydrocarbons to serve as the oil for mixing with the comminuted bituminous coal to' form said paste mixture.

3; A continuous process for the production of light and medium hydrocarbon oils from bituminous coal which consists in mixing the coal in finely comminuted form with a heavy oil to form a paste mixture, forcing the paste mixture through a continuous enclosed passage comprising a plurality of successively arranged treatment zones, maintaining a pressure of at least of the order of 20 kg./cm.2 in said enclosed passage whilst the mixture is forced therethrough, heating the mixture rapidly to a temperature approximating to the lowest conversion temperature of the coal whilst it is passing through a first treatment zone, applying heat at such a rate to the mixture whilst it is continuously passing through a second treatment zone of larger volume than said first treatment zone that the temperature of the mixture will be maintained substantially at said lowest conversion temperature, the Volume of said second treatment zone being such that the conversion at said temperature will be substantially completed during the passage of the mixture through said second treatment zone, applying heat at such a rate to said modified mixture as it passes continuously through a third treatment zone of smaller volume than said second treatment zone that the temperature of the modified mixture will be raised during its passage through said third treatment zone to a temperature approximating to a higher conversion temperature of the coal but below the cracking temperature, applying heat at such a rate to the modified mixture whilst it is continuously passing through a fourth treatment Zone of larger volume than said third treatment zone that the temperature of the modified mixture will be maintained substantially at said higher conversion temperature, the Volume of said fourth treatment Zone being such that the conversion at said higher conversion temperature will be substantially completed during the passage of the modified mixture through said fourth treatment zone, applying heat at such a rate to said further modified mixture as it passes continuously through a fifth treatment zone of smaller volume than said fourth treatment zone that the temperature of the further modied mixture will be raised during its passage through said fifth treatment zone to a temperature approximating to a cracking temperature, applying heat at such a rate to the further modilied mixture whilst it is continuously passing through a sixth treatment zone of larger volume than said fth treatment zone that the temperature of the further modilled mixture will be maintained substantially at said cracking temperature, the volume of said sixth treatment zone being such as to permit cracking at such temperature to be substantially completed during the passage of the mixture through said sixth treatment zone, discharging the cracked mixture from said sixth treatment zone with release of pressure, and condensing and collecting the liquid hydrocarbons.

4. A continuous process for the production of light andl medium hydrocarbon oils from bituminous coal which consists in mixing the coal in finely comminuted form with a heavy oil to form a paste mixture, forcing the mixture through a continuous enclosed passage comprising a plurality of successively arranged treatment zones, maintaining a pressure of at least of the order of 20 kg./cm.2 in said enclosed passage whilst the mixture is forced therethrough, heating the mixture rapidly to a temperature of about 300 C. whilst it is passing through a first treatment zone, applying heat at such a rate to the mixture -whilst it is continuously passing through a second treatment zone of larger volume than said first treatment zone that the temperature of the mixture will be maintained substantially at 300 C., the volume of said second treatment Zone being such that the conversion at said temperature will be substantially completed during the passage of the mixture through said second treatment zone, applying heat at such a rate to said modified mixture as it passes continuously through a third treatment zone of smaller volume than said second treatment zone that the temperature of the modified mixture will'be raised during its passage through said third treatment zone to a temt perature'of about 400 C., applying heat at such a rate to the modified mixture whilst it is continuously passing through a fourth treatment zone of larger volume than said third treatment zone that the temperature of the modified mixture will be maintained substantially at 400 C., the volume of said fourth treatment zone being such that the conversion at said temperature of 400 C. will be substantially completed during the passage of the modied mixture through said fourth treatment Zone, applying heat at such a rate to said further modified mixture as it passes, .continucusly throush a. fifth treatment zone 0f smaller volumethan said fourth treatment zone that the temperature ofthe further modified mixture will be raised temperature of the further modified mixture will be maintained substantially at 450 C., the volume of said sixth treatment Zone being such as to permit cracking at such temperature to be substantially completed during the passage of the mixture through said sixth treatment zone, discharging the cracked mixture from said sixth treatment 4z one with Vrelease of pressure, and condensing and collect-ing the liquid hydrocarbons.

5. Proeess'as claimed in claim 4, wherein the cracked mixture is selectively discharged into one of a plurality of retorts whilst removing and separating the volatile components from the non-volatile residues until the retort is filled to the desired extent whereupon the cracked mixture is discharged into a further one of said retorts, heating the filled retort to heat the non-volatile residues therein to a `coking temperature of between 500 C. and 1000 C. to release further vvolatile components, condensing ,and collecting said volatile components, and removing the formed coke from said retort.

6. A continuous process for obtaining a high output of low-boiling liquid hydrocarbons from bituminous coal, which comprises the steps of mixing bituminous coal in comminuted form with hydrocarbon oil to produce a pastelike mixture, forcing said Imixture along a continuous passage, heating said mixture in an initial section of said passage to a temperature between 280 and 310 C. while maintaining a pressure of at least 20 kg./crn.2, maintaining such temperature and pressure for a period in the order of 30 minutes in a second section of said passage, further heating, in a third section of said passage, the liquidmixture obtained to a higher temperature between 390 and 410 C., maintaining in a fourth section of said .passage such higher temperature for a further period in the order Vof 30 minutes while still maintaining said pressure, to convert the greater part of the coal into an oil-dissolved extract, and subjecting such oil-dissolved extract to pressure cracking in further sections of saidY passage.

.References Cited in the file of this patent VUNITED STATES PATENTS 

1. A CONTINUOUS PROCESS FOR THE PRODUCTION OF LIGHT AND MEDIUM HYDROCARBON OILS AND HARD COKE FROM BITUMINOUS COAL WHICH CONSISTS INMIXING THE COAL IN FINELY COMMINUTED FORM WITH A HEAVY OIL TO FORM A PASTE MIXTURE, FORCING THE MIXTURE THROUGH A CONTINUOUS ENCLOSED PASSAGE COMPRISING A PLURALITY OF SUCCESSIVELY ARRANGED TREATMENT ZONES, MAINTAINING A PRESSURE OF AT LEAST OF THE ORDER 20 KG./CM. 2 IN SAID ENCLOSED PASSAGE WHILST THE MIXTURE IS FORCED THERETHROUGH, HEATING THE MIXTURE RAPIDLY TO A TEMPERATURE APPROXIMATELY TO THE LOWEST CONVERSION TEMPERATURE OF THE COAL WHILST IT IS PASSING THROUGH A FIRST TREATMENT ZONE, APPLYING HEAT AT SUCH A RATE TO THE MIXTURE WHILST IT IS CONTINUOUSLY PASSING THROUGH A SECOND TREATMENT ZONE OF LARGER VOLUME THAN SAID FIRST TREATMENT ZONE THAT THE TEMPERATURE OF THE MIXTURE WILL BE MAINTAINED SUBSTANTIALLY AT SAID LOWEST CONVERSION TEMPERATURE, THE VOLUME OF SAID SECOND TREATMENT ZONE BEING SUCH THAT THE CONVERSION AT SAID TEMPERATURE WILL BE SUBSTANTIALLY COMPLETED DURING THE PASSAGE OF THE MIXTURE THROUGH SAID SECOND TREATMENT ZONE, APPLYING HEAT AT SUCH A RATE TO SAID MODIFIED MIXTURE AS IT PASSES CONTINUOUSLY THROUGH A THIRD TREATMENT ZONE OF SMALLER VOLUME THAN SAID SECOND TREATMENT ZONE THAT THE TEMPERATURE OF THE MODIFIED MIXTURE WILL RAISED DURING ITS PASSAGE THROUGH SAID THIRD TREATMENT ZONE TO A TEMPERATURE APPROXIMATELY TO A HIGHTER CONVERSION TEMPERATURE OF THE COAL BUT BELOW THE CRACKING TEMPERATURE, APPLYING HEAT AT SUCH A RATE TO THE MODIFIED MIXTURE WHILST IT IS CONTINUOUSLY PASSING THROUGH A FOURTH TREATMENT ZONE OF LARGER VOLUME THAN SAID THIRD TREATMENT ZONE THAT THE TEMPERATURE OF THE MODIFIED MIXTURE WILL BE MAINTAINED SUBSTANTIALLY AT SAID HIGHER CONVERSION TEMPERATURE, THE VOLUME OF SAID FOURTH TREATMENT ZONE BEING SUCH THAT THE CONVERSION AT SAID HIGHER CONVERSION TEMPERATURE WILL BE SUBSTANTIALLY COMPLETED DURING THE PASSAGE OF THE MODIFIED MIXTURE THROUGH SAID FOURTH TREATMENT ZONE, APPLYING HEAT AT SUCH A RATE TO SAID FURTHER MODIFIED MIXTURE AS IT PASSES CONTINUOUSLY THROUGH A FIFTH TREATMENT ZONE OF SMALLER VOLUME THAN SAID FOURTH TREATMENT ZONE THAT THE TEMPERATURE OF THE FURTHER MODIFIED MIXTURE WILL BE RAISED DURING ITS PASSAGE THROUGH SAID FIFTH TREATMENT ZONE TO A TEMPERATURE APPROXIMATING TO A CRACKING TEMPERATURE, APPLYING HEAT AT SUCH A RATE TO THE FURTHER MODIFIED MIXTURE WHILST IT IS CONTINUOUSLY PASSING THROUGH A SIXTH TREATMENT ZONE OF LARGER VOLUME THAN SAID FIFTH TREATMENT ZONE THAT THE TEMPERATURE OF THE FURTHER MODIFIED MIXTURE WILL BE MAINTAINED SUBSTANTIALLY AT SAID CRACKING TEMPERATURE, THE VOLUME OF SAID SIXTH TREATMENT ZONE BEING SUCH AS TO PERMIT CRACKING AT SUCH TEMPERATURE TO BE SUBSTANTIALLY COMPLETED DURING THE PASSAGE OF THE MIXTURE THROUGH SAID SIXTH TREATMENT ZONE, DISCHARGING THE CRACKED MIXTURE FROM SAID SIXTH TREATMENT ZONE WITH RELEASE OF PRESSURE INTO ONE OF A PLURALITY OF RETORTS WHILST REMOVING AND SEPARATING THE VOLATILE COMPONENTS FROM THE NON-VOLATILE RESIDUES UNTIL THE RETORT IS FILLED TO THE DESIRED EXTENT WHEREUPON THE CRACKED MIXTURE IS DISCHARGED INTO A FURTHER ONE OF SAID RETORTS, HEATING THE FILLED RETORT TO HEAT THE NON-VOLATILE RESIDUES THEREIN TO A COKING TEMPERATURE AND RELEASE FURTHER VOLATILE COMPONENTS, COLLECTING THE VOLATILE COMPONENTS, AND REMOVING THE FORMED COKE FROM SAID RETORT. 